| License Code | Description | Target Species |
|---|---|---|
| al | Aquaculture License: Established in 2017 | Aquaculture |
| cfc | Commercial fishing crew | Finfish |
| cfs | Commercial fishing single | Finfish |
| cpc | Commercial pelagic and anadromous crew | Pelagic/Anadromous |
| cps | Commercial pelagic and anadromous single | Pelagic/Anadromous |
| cs | Commercial Shellfish | Shellfish |
| csc | Commercial shrimp crew | Shrimp |
| cso | Commercial shellfish + 70 | Shrimp |
| css | Commerical Shrimp Single | Shrimp |
| csu | Commercial Shellfish Under 18 | Shellfish |
| csw | Commercial Shrimp Single | Shrimp |
| csws | Commercial Shrimp Crew | Shrimp |
| e0 | Elver Dip Net | Elver |
| e0c | Elver Dip Net Crew | Elver |
| e1 | Elver 1 Fyke Net | Elver |
| e1c | Elver 1 Fyke Net Crew | Elver |
| e2 | Elver 2 Fyke Net | Elver |
| e29 | Elver Non Resident | Elver |
| e2c | Elver 2 Fyke Net with Crew | Elver |
| e6 | Elver Dip Net 1 Fyke Net | Elver |
| e6c | Elver Dip Net 1 Fyke Net Crew | Elver |
| eel | Eel license - changed to Eel Pot | Eel |
| eex | Elver Exporter | Elver |
| elv | Elver | Elver |
| ep | eel pot/hoop net | Eel |
| fhc | federal halibut crew | Halibut |
| gc | Green crab | Green crab |
| gcn | green crab non resident | Green crab |
| la | Lobster Crab Apprentice | Lobster |
| lao | Lobster Crab Apprentice + 70 | Lobster |
| lau | lobster crab apprentace under 18 | Lobster |
| lc1 | Lobster crab class I | Lobster |
| lc2 | Lobster crab class II | Lobster |
| lc2o | Lobster crab class II + 70 | Lobster |
| lc3 | Lobster crab class III | Lobster |
| lc3o | Lobster crab class III + 70 | Lobster |
| lco | Lobster Crab + 70 | Lobster |
| lcs | Lobster Crab Student - policy change in 2016 | Lobster |
| lcu | Lobster Crab Under 18 | Lobster |
| lnc | Lobster crab non commerical | Lobster |
| mb | Mussel Boat | Mussel |
| md | Mussel Dragger | Mussel |
| menc | menhaden commercial | Menhaden |
| mennr | menhaden commercial non-res | Menhaden |
| menr | menhaden non commercial | Menhaden |
| mh | Mussel Hand | Mussel |
| mwd | Marine Worm Digging | Marine worm |
| ncf | commercial fishing non resident | Finfish |
| ncp | non-resident pelagic and anadromous | Pelagic/Anadromous |
| ncs | Scallop non commericial | Scallop |
| nfhc | non federal halibut crew | Halibut |
| nfhs | non federal halibut single | Halibut |
| nla | Non-res lobster apprentice | Lobster |
| nlc1 | Non-res lobster class 1 | Lobster |
| nrlp | Non-res lob crab landing | Lobster |
| nrs | Seaweed non resident | Seaweed |
| nrss | seaweed non resident supp | Seaweed |
| ntp | non-resident tuna permit | Tuna |
| qm | Quahog (Mahogany) | Quahog clam |
| sb | Scallop boat - from 1990 to 1993 - then went to SB | Scallop |
| scd | Sea Cucumber Drag | Sea cucumber |
| sd | Scallop Dragger | Scallop |
| sdi | Scallop diver | Scallop |
| sh | Scallop Hand - now SDI changed in 1994 | Scallop |
| spt | spat | Spat |
| sub | Sea Urchin Dragger | Sea urchin |
| suh | Sea urchin diver | Sea urchin |
| sur | Sea Urchin Raking | Sea urchin |
| surf | Surf Clam Boat | Surf clam |
| sw | Seaweed | Seaweed |
| swbn | Nonresident Seaweed Buyer | Seaweed |
| sws | seaweed supplemental | Seaweed |
Species Networks
Species Grouping
To correlate species distribution changes with changes in license holdings in Maine, license types have been grouped by target species as described by Maine State Legislation.
License Portfolio by Species
Using Theresa Burnham’s code for building the individual license portfolio, license types were grouped by target species. A binary matrix was created, whereas 1 denotes an individual license holding for a corresponding year and 0 denotes no license held. With this co-occurrence matrix, we can quantify which license types were held together over the past 30 years and how those holdings have changed.
Species Proportions
Species Matrix
| Species | Aquaculture | Eel | Elver | Finfish | Green crab | Halibut | Lobster | Marine worm | Menhaden | Mussel | Pelagic/Anadromous | Quahog clam | Scallop | Sea cucumber | Sea urchin | Seaweed | Shellfish | Shrimp | Spat | Surf clam | Tuna |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Aquaculture | 0 | 3 | 5 | 33 | 43 | 0 | 293 | 13 | 29 | 23 | 17 | 1 | 34 | 0 | 9 | 26 | 149 | 15 | 40 | 0 | 0 |
| Eel | 3 | 0 | 173 | 270 | 74 | 0 | 260 | 60 | 11 | 55 | 38 | 35 | 72 | 0 | 58 | 88 | 140 | 45 | 0 | 13 | 0 |
| Elver | 5 | 173 | 0 | 1793 | 121 | 1 | 4646 | 1067 | 65 | 147 | 95 | 36 | 1261 | 0 | 1373 | 194 | 3206 | 326 | 0 | 0 | 0 |
| Finfish | 33 | 270 | 1793 | 0 | 463 | 17 | 29510 | 1758 | 10145 | 670 | 5480975 | 652 | 10182 | 54 | 6093 | 1206 | 6205 | 4968 | 21 | 8 | 2 |
| Green crab | 43 | 74 | 121 | 463 | 0 | 0 | 754 | 254 | 39 | 64 | 80 | 42 | 258 | 5 | 115 | 169 | 656 | 134 | 5 | 6 | 0 |
| Halibut | 0 | 0 | 1 | 17 | 0 | 0 | 21 | 0 | 2 | 0 | 5 | 0 | 3 | 0 | 0 | 0 | 3 | 0 | 0 | 0 | 0 |
| Lobster | 293 | 260 | 4646 | 29510 | 754 | 21 | 0 | 3933 | 2262 | 982 | 1732 | 994 | 21390 | 72 | 12567 | 1555 | 16165 | 6715 | 66 | 42 | 1 |
| Marine worm | 13 | 60 | 1067 | 1758 | 254 | 0 | 3933 | 0 | 12 | 93 | 33 | 58 | 976 | 0 | 1175 | 589 | 5552 | 155 | 0 | 2 | 0 |
| Menhaden | 29 | 11 | 65 | 10145 | 39 | 2 | 2262 | 12 | 0 | 15 | 5310 | 24 | 291 | 2 | 53 | 32 | 187 | 4 | 18 | 4 | 0 |
| Mussel | 23 | 55 | 147 | 670 | 64 | 0 | 982 | 93 | 15 | 0 | 44 | 189 | 916 | 18 | 451 | 287 | 465 | 154 | 3 | 14 | 0 |
| Pelagic/Anadromous | 17 | 38 | 95 | 5480975 | 80 | 5 | 1732 | 33 | 5310 | 44 | 0 | 45 | 567 | 15 | 133 | 88 | 211 | 394 | 11 | 7 | 0 |
| Quahog clam | 1 | 35 | 36 | 652 | 42 | 0 | 994 | 58 | 24 | 189 | 45 | 0 | 1186 | 8 | 619 | 52 | 257 | 184 | 2 | 15 | 0 |
| Scallop | 34 | 72 | 1261 | 10182 | 258 | 3 | 21390 | 976 | 291 | 916 | 567 | 1186 | 0 | 114 | 9837 | 621 | 4263 | 2549 | 12 | 17 | 0 |
| Sea cucumber | 0 | 0 | 0 | 54 | 5 | 0 | 72 | 0 | 2 | 18 | 15 | 8 | 114 | 0 | 54 | 0 | 3 | 29 | 0 | 0 | 0 |
| Sea urchin | 9 | 58 | 1373 | 6093 | 115 | 0 | 12567 | 1175 | 53 | 451 | 133 | 619 | 9837 | 54 | 0 | 606 | 4156 | 769 | 2 | 0 | 0 |
| Seaweed | 26 | 88 | 194 | 1206 | 169 | 0 | 1555 | 589 | 32 | 287 | 88 | 52 | 621 | 0 | 606 | 0 | 773 | 163 | 4 | 13 | 0 |
| Shellfish | 149 | 140 | 3206 | 6205 | 656 | 3 | 16165 | 5552 | 187 | 465 | 211 | 257 | 4263 | 3 | 4156 | 773 | 0 | 520 | 9 | 9 | 0 |
| Shrimp | 15 | 45 | 326 | 4968 | 134 | 0 | 6715 | 155 | 4 | 154 | 394 | 184 | 2549 | 29 | 769 | 163 | 520 | 0 | 0 | 6 | 0 |
| Spat | 40 | 0 | 0 | 21 | 5 | 0 | 66 | 0 | 18 | 3 | 11 | 2 | 12 | 0 | 2 | 4 | 9 | 0 | 0 | 0 | 0 |
| Surf clam | 0 | 13 | 0 | 8 | 6 | 0 | 42 | 2 | 4 | 14 | 7 | 15 | 17 | 0 | 0 | 13 | 9 | 6 | 0 | 0 | 0 |
| Tuna | 0 | 0 | 0 | 2 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Annual Species Metrics
Degree and betweenness are both ways of measuring centrality.
“The degree of a node is the number of other nodes that single node is connected to.
Important nodes tend to have more connections to other nodes. Highly connected nodes are interpreted to have high degree centrality.”
“[Betweenness] ranks the nodes based on the flow of connections through the network. Importance is demonstrated through high frequency of connection with multiple other nodes. Nodes with high levels of betweenness tend to serve as a bridge for multiple sets of other important nodes.” Source
Lobster is the most abundant license type held in Maine, its high degree of centrality with relatively low betweenness suggests that while lobster has a lot of connections to other license types, those license types that co-occur with lobster don’t co-occur with many other license types.
Eel and quahog have highly variable betweenness with relatively low degree of centrality, suggesting that these license may be held concurrently with more central license types to supplement harvest.
Finfish also has a high degree of centrality and low betweeness.
Annual Network Plots
Similar to plotting the license holdings as a network over time, we plot the target species pertaining to these permits over time. This makes for a more easily interpretable graph, as well as increased potential for correlating license changes to species distribution changes